If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
I'd like to challenge the view that 6x9 folders give soft pictures
RolandRB wrote:
I'd like to challenge the view that 6x9 folders give soft pictures. I've heard this opinion oft repeated on websites that discuss medium format. The view is that "the film is not flat" and so gives poor results. I challenge that. I've just got the results back from a 1931 6x9 Zeiss Ikonta and there is no evidence of lack of film flatness leading to poor focus. Because the camera is old, I tightened the springs on the pressure plate before taking any photos and I always wind on just before taking the shot, because it is only natural for the film to warp over the plate in the heat over time, so I avoid that. If I delay taking a photo after winding on - maybe waiting for better light or sky - then I start to wind on to tighten the film and then I get no problem. If it were just the 'wind on' need, that would be of little concern. From the various replies to my enquiry some time ago, I think there is also the issue of RF focus errors to take into account. This is what scared me off buying a used one a few months ago. |
#2
|
|||
|
|||
I'd like to challenge the view that 6x9 folders give soft pictures
"Alan Browne" wrote in message ... RolandRB wrote: I'd like to challenge the view that 6x9 folders give soft pictures. I've heard this opinion oft repeated on websites that discuss medium format. The view is that "the film is not flat" and so gives poor results. I challenge that. I've just got the results back from a 1931 6x9 Zeiss Ikonta and there is no evidence of lack of film flatness leading to poor focus. Because the camera is old, I tightened the springs on the pressure plate before taking any photos and I always wind on just before taking the shot, because it is only natural for the film to warp over the plate in the heat over time, so I avoid that. If I delay taking a photo after winding on - maybe waiting for better light or sky - then I start to wind on to tighten the film and then I get no problem. If it were just the 'wind on' need, that would be of little concern. From the various replies to my enquiry some time ago, I think there is also the issue of RF focus errors to take into account. This is what scared me off buying a used one a few months ago. The Super Ikonta has a very good rangefinder. Probably, in a camera this old, it may need some adjustment, mostly to make sure the infinity point is set properly. It is an error to think that flare exists only for back lighted scenes the flare in uncoated lenses is there all the time. The amount depends on the number of air-glass surfaces and goes up exponentially as the number of surfaces increases. For a relatively simple lens like a Tessar the flare is not bad. Backlighting can bring out other sources of flare such as reflections from the lens mount and from the insides of the camera. Those are also always present but strong light within the image area can make them more of a problem. In general a good uncoated Tessar has pretty good contrast. The Tessar in the Ikonta series is a front element focusing lens. This is a very elementary zoom lens whose focal length is changed to change focus. The problem is that the corrections for aberrations change with the change in focus and there is nothing in these simple lenses to compensate for it. In general front element focusers are designed to have the best correction at distant focus because the assumption is that one will want the best rendition of detail there. Nonetheless, the Super-Ikonta series has an excellent reputation for sharpness. BTW, since the focal length of the lens is changed to effect focus the viewing angle remains constant with distance. For that reason a fixed finder such as used on the Super-Ikonta is accurate at all distances (other than for parallax). -- Richard Knoppow Los Angeles, CA, USA |
#3
|
|||
|
|||
I'd like to challenge the view that 6x9 folders give soft pictures
"Richard Knoppow" wrote in message m... "Alan Browne" wrote in message ... RolandRB wrote: I'd like to challenge the view that 6x9 folders give soft pictures. I've heard this opinion oft repeated on websites that discuss medium format. The view is that "the film is not flat" and so gives poor results. I challenge that. I've just got the results back from a 1931 6x9 Zeiss Ikonta and there is no evidence of lack of film flatness leading to poor focus. Because the camera is old, I tightened the springs on the pressure plate before taking any photos and I always wind on just before taking the shot, because it is only natural for the film to warp over the plate in the heat over time, so I avoid that. If I delay taking a photo after winding on - maybe waiting for better light or sky - then I start to wind on to tighten the film and then I get no problem. If it were just the 'wind on' need, that would be of little concern. From the various replies to my enquiry some time ago, I think there is also the issue of RF focus errors to take into account. This is what scared me off buying a used one a few months ago. The Super Ikonta has a very good rangefinder. Probably, in a camera this old, it may need some adjustment, mostly to make sure the infinity point is set properly. It is an error to think that flare exists only for back lighted scenes the flare in uncoated lenses is there all the time. The amount depends on the number of air-glass surfaces and goes up exponentially as the number of surfaces increases. For a relatively simple lens like a Tessar the flare is not bad. Backlighting can bring out other sources of flare such as reflections from the lens mount and from the insides of the camera. Those are also always present but strong light within the image area can make them more of a problem. In general a good uncoated Tessar has pretty good contrast. The Tessar in the Ikonta series is a front element focusing lens. This is a very elementary zoom lens whose focal length is changed to change focus. The problem is that the corrections for aberrations change with the change in focus and there is nothing in these simple lenses to compensate for it. In general front element focusers are designed to have the best correction at distant focus because the assumption is that one will want the best rendition of detail there. Nonetheless, the Super-Ikonta series has an excellent reputation for sharpness. BTW, since the focal length of the lens is changed to effect focus the viewing angle remains constant with distance. For that reason a fixed finder such as used on the Super-Ikonta is accurate at all distances (other than for parallax). -- Richard Knoppow Los Angeles, CA, USA Another BTW, I rather think that focus problems attributed to film flatness are often actually due to focus shift. I've found that even some very good lenses (Zeiss Tessar, Kodak Ektar) have enough shift to affect the accuracy of focus on a Speed Graphic using a rangefinder. This would also apply to other types of cameras that do not show focus directly at the f/stop used. Focus shift comes from residual spherical aberration which is affected by the stop. Usually, when stopped down perhaps two stops from maximum, most of the spherical is gone. If a lens is focused as best as possible when wide open and then stopped down a couple of stops one finds that the point of best focus may have changed. This effect is relatively large for lenses like the Goerz Dagor, which as a large residual of spherical, is less for Tessars, depending on the exact design, and is minimal for the six element lenses of the Biotar type and more complex lenses based on it commonly used in 35mm cameras. -- Richard Knoppow Los Angeles, CA, USA |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
I'd like to challenge the view that 6x9 folders give soft pictures | Toni Nikkanen | Medium Format Photography Equipment | 0 | July 8th 09 07:44 AM |
[Mpix Challenge] Megapixel resolution challenge | Alan Browne | Digital SLR Cameras | 50 | December 10th 08 09:46 PM |
FS: Nikon 52mm Soft Filters - Soft 1 and Soft 2 | Joe Pucillo | General Equipment For Sale | 0 | March 16th 05 04:11 AM |
FS: Nikon 52mm Soft Filters - Soft 1 and Soft 2 | Joe Pucillo | 35mm Equipment for Sale | 0 | March 16th 05 04:11 AM |
FS: Nikon 52mm Soft Filters - Soft 1 and Soft 2 | Joe Pucillo | Digital Photo Equipment For Sale | 0 | March 16th 05 04:11 AM |